Transgenic potato plants depleted for the major tuber protein patatin via expression of antisense RNA

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Patatin, one of the major potato tuber proteins, is a glycoprotein of approx. 40 kDa and contributes 20% of the water soluble protein fraction of tubers of the potato cultivar Désirée. Despite a detailed molecular and biochemical analysis, no definitive physiological role has been assigned to the protein. In order to approach this question, we reduced the amount of patatin in potato tubers by Agrobacterium-mediated introduction of a chimeric gene containing a class I patatin cDNA cloned in reverse orientation to the 35S CaMV promoter into potato plants, thus resulting in formation of patatin antisense RNA. In several transformants the amount of patatin protein and RNA is drastically reduced, the maximum level being about 90% reduction in case of the protein and 99% in case of the RNA. This reduction of patatin protein in tubers of transgenic potato plants does not lead to readily visible changes in phenotype and development, rather the plants are indistinguishable from controls. Whereas no antisense RNA and only trace amounts of sense RNA were detected in tubers of inhibited plants, both sense and antisense RNA could be detected in leaf tissue of these plants. Induction of expression of the endogenous patatin genes in leaves by incubation of detached leaves in sucrose leads to a reduction of the level of antisense RNA. This can be interpreted as evidence for a direct interaction between sense and antisense RNA.